Download UNIVERSITY OF CAMBRIDGE INTERNATIONAL

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS
General Certificate of Education
Advanced Subsidiary Level and Advanced Level
*2154760135*
9700/02
BIOLOGY
Paper 2 Structured Questions AS
October/November 2008
1 hour 15 minutes
Candidates answer on the Question Paper.
Additional Materials:
Electronic calculator
Ruler (cm/mm)
READ THESE INSTRUCTIONS FIRST
Write your Centre number, candidate number and name in the spaces provided at the top of this page.
Write in dark blue or black pen.
You may use a soft pencil for any diagrams, graphs or rough working.
Do not use staples, paper clips, highlighters, glue or correction fluid.
DO NOT WRITE IN ANY BARCODES.
Answer all questions.
At the end of the examination, fasten all your work securely together.
The number of marks is given in brackets [ ] at the end of each question or part question.
For Examiner’s Use
1
2
3
4
5
6
Total
This document consists of 15 printed pages and 1 blank page.
SP (SHW 00336 7/08) V00741/2
© UCLES 2008
[Turn over
2
Answer all the questions.
1
For
Examiner’s
Use
Receptor proteins are part of the fluid mosaic structure of cell surface (plasma) membranes of
T-lymphocytes. Each type of receptor protein is specific to a particular antigen.
Fig. 1.1 shows a receptor protein and the surrounding phospholipids of a cell surface
membrane of a T-lymphocyte.
antigen
Fig. 1.1
(a) (i)
(ii)
Draw a bracket ( } ) on Fig. 1.1 to indicate the width of the phospholipid bilayer.
[1]
Explain the term fluid mosaic.
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
............................................................................................................................ [2]
© UCLES 2008
9700/02/O/N/08
3
(iii)
Describe how the structure of the receptor shown in Fig. 1.1 is similar to the
structure of an antibody molecule.
For
Examiner’s
Use
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
............................................................................................................................ [2]
(b) Describe the roles of T-lymphocytes in a primary immune response.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
.................................................................................................................................... [4]
(c) Describe three functions of cell surface membranes, other than the recognition of
antigens.
1 .......................................................................................................................................
..........................................................................................................................................
2 .......................................................................................................................................
..........................................................................................................................................
3 .......................................................................................................................................
.................................................................................................................................... [3]
[Total: 12]
© UCLES 2008
9700/02/O/N/08
[Turn over
4
2
Polysaccharides, such as glycogen, amylopectin and amylose, are formed by polymerisation
of glucose. Fig. 2.1 shows part of a glycogen molecule.
X
Fig. 2.1
(a) With reference to Fig. 2.1,
(i)
describe how the structure of glycogen differs from the structure of amylose;
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
............................................................................................................................ [2]
(ii)
describe the advantages for organisms in storing polysaccharides, such as
glycogen, rather than storing glucose.
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
............................................................................................................................ [3]
© UCLES 2008
9700/02/O/N/08
For
Examiner’s
Use
5
(b) Glycogen may be broken down to form glucose.
For
Examiner’s
Use
Fig. 2.2 shows region X from the glycogen molecule in Fig. 2.1 in more detail.
CH2OH
O
H
CH2OH
H
H
OH
H
H
OH
HO
O
H
O
CH2OH
H
H
OH
H
H
OH
O
H
O
CH2OH
H
H
OH
H
H
OH
O
H
O
H
H
OH
H
H
OH
O
Fig. 2.2
Draw an annotated diagram in the space provided to explain how a glucose molecule is
formed from the free end of the glycogen molecule shown in Fig. 2.2.
[3]
[Total: 8]
© UCLES 2008
9700/02/O/N/08
[Turn over
6
3
Trypsin is a protease enzyme, which hydrolyses protein molecules, such as albumen, to
amino acids.
A student investigated the effect of substrate concentration on the activity of trypsin. Six
different concentrations of albumen were prepared and trypsin was added to each in turn.
The student measured the time for albumen to break down and then calculated the rate of
reaction. The investigation was carried out at 35 °C.
The student’s results are shown in Fig. 3.1.
18
16
14
12
rate of
10
reaction /
arbitrary
8
units
6
4
2
0
0
5
10
15
20
25
30
35
substrate concentration / g dm–3
Fig. 3.1
(a) Explain the results shown in Fig. 3.1.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
.................................................................................................................................... [3]
(b) The student repeated the investigation at 25 °C.
Draw on Fig. 3.1 a curve to show the results that you would expect.
© UCLES 2008
9700/02/O/N/08
[2]
For
Examiner’s
Use
7
During infections of the lungs, phagocytes move from the blood to the lining of the alveoli.
Phagocytes release the enzyme elastase (a protease) in order to digest a pathway through
the alveolar wall. Most people produce a glycoprotein, alpha 1-antitrypsin (AAT), in the lung
which inhibits elastase and so prevents widespread breakdown of alveoli. The inhibitory
action of AAT was investigated using the enzyme trypsin.
For
Examiner’s
Use
(c) Describe one way in which AAT may act to inhibit the enzyme elastase.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
.................................................................................................................................... [3]
(d) Explain how you would adapt the student’s investigation with trypsin to find out how AAT
acts as an inhibitor.
You may use the space below to sketch the graph of the results that you might expect.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
rate of reaction
substrate concentration
[4]
© UCLES 2008
9700/02/O/N/08
[Turn over
8
(e) Elastase breaks down the protein elastin. Describe the function of elastin in the lungs.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
.................................................................................................................................... [2]
(f)
Tobacco smoke inactivates AAT. In long-term smokers this can result in the breakdown
of much of the elastin in the lungs.
State the name of the condition that results from breakdown of elastin that occurs in
some long-term smokers.
.................................................................................................................................... [1]
[Total: 15]
© UCLES 2008
9700/02/O/N/08
For
Examiner’s
Use
9
4
Phloem transfer cells are specialised companion cells that load sucrose into sieve tube
elements.
For
Examiner’s
Use
Fig. 4.1 is an electron micrograph of a transverse section showing phloem tissue from a leaf
of Senecio vulgaris. The section shows two sieve tube elements and four phloem transfer
cells. The sieve tube elements are small in this section because it is taken at the end of a
vein in the leaf.
It is thought that the many ingrowths of the cell walls visible in Fig. 4.1 are related to the
movement of large quantities of sucrose.
cell wall
ingrowths in
transfer cells
cell wall
ingrowths in
transfer cells
sieve tube
elements
magnification = × 10,000
Fig. 4.1
© UCLES 2008
9700/02/O/N/08
[Turn over
10
(a) Describe how companion cells load sucrose into phloem sieve tubes.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
.................................................................................................................................... [4]
(b) Transfer cells move large quantities of sucrose into phloem sieve tubes.
Suggest why these cells have cell wall ingrowths as shown in Fig. 4.1.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
.................................................................................................................................... [2]
(c) (i)
Explain the advantage of studying cells, such as transfer cells, with the electron
microscope rather than the light microscope.
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
............................................................................................................................ [2]
(ii)
Describe the appearance of the phloem sieve tubes when viewed in longitudinal
section.
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
............................................................................................................................ [2]
[Total: 10]
© UCLES 2008
9700/02/O/N/08
For
Examiner’s
Use
11
5
Plasmodium falciparum is the causative agent of the most severe form of malaria.
For
Examiner’s
Use
It is distributed throughout the tropics.
(a) Explain why malaria is restricted to the tropics.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
.................................................................................................................................... [2]
© UCLES 2008
9700/02/O/N/08
[Turn over
12
The haploid number of P. falciparum is 14.
For
Examiner’s
Use
Fig. 5.1 shows the life cycle of P. falciparum.
stages of
life cycle in human host
mitosis
infective stage enters human
host when mosquito takes
a blood meal
cells taken up by
mosquito when feeding
on an infected human
B
female
gamete
male
gametes
A
zygote
mitosis
reduction division
(meiosis)
Fig. 5.1
(b) (i)
State the number of chromosomes present at stages A and B.
A ...............................................................................................................................
B ......................................................................................................................... [2]
© UCLES 2008
9700/02/O/N/08
13
(ii)
Explain why a reduction division (meiosis) occurs during the life cycles of organisms,
such as Plasmodium, that reproduce sexually.
For
Examiner’s
Use
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
............................................................................................................................ [2]
(c) Explain why it has proved difficult to develop a vaccine for malaria.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
.................................................................................................................................... [4]
[Total: 10]
© UCLES 2008
9700/02/O/N/08
[Turn over
14
6
The element nitrogen is present in many biological molecules, such as amino acids, proteins
and nucleotides.
Fig. 6.1 shows part of the nitrogen cycle.
nitrogen (N2)
in the atmosphere
D
E
nitrate ions
in the soil
nitrite ions
in the soil
F
C
ammonium
ions in soil
amino acids
in plants
urea in
urine
urea
protein
in plants
A
amino acids
in animals
Fig. 6.1
© UCLES 2008
9700/02/O/N/08
B
protein
in animals
For
Examiner’s
Use
15
The statements 1 to 10 are processes that occur during the nitrogen cycle.
For each of the stages B to F shown on Fig. 6.1, select the appropriate description from the
list of statements and write it in the box provided.
Write only one number in each box.
The first one (A) has been selected and completed for you.
1
digestion by primary consumers
A
1
2
amino acid synthesis in plants
B
………
3
protein synthesis in primary consumers
C
………
4
nitrification
D
………
5
decomposition
E
………
6
nitrogen fixation
F
7
excretion
………
8
deamination in primary consumers
9
denitrification
10 deamination by bacteria and fungi
[Total: 5]
© UCLES 2008
9700/02/O/N/08
For
Examiner’s
Use
16
BLANK PAGE
Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every
reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the
publisher will be pleased to make amends at the earliest possible opportunity.
University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of
Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.
9700/02/O/N/08